In general, water-emulsifiable leather and fur fatting agents and lubricants are produced by sulfating unsaturated natural or synthetic fats, oils, or waxes with the usual sulfating agents, such as commercial sulfuric acid or oleum. As a rule, sulfation is continued only until sufficient emulsifiability is attained and the sulfation products obtained still have a considerable iodine number. However, the unsaturated character of these products unfavorably influences their oxidation stability and, hence, the shelf life of the lubricants as well as the light resistance of the leather and furs lubricated with them. Furthermore, the sulfuric acid esters formed by sulfation have little resistance to acid action in the leather and readily become saponified, thereby making it possible for free fatty acids to form and, if saturated fatty acids are present in sufficient quantity, fatty acid exudation to develop.
This drawback is eliminated, according to U.S. Pat. No. 3,370,005, by reducing the number of double bonds by 20 to 70 percent by partial chlorination of the unsaturated raw materials. The subsequent sulfation yields lubricants with improved properties regarding light resistance and shelf life, but even these products are sensitive to acid and not entirely stable in storage.
Leather lubricants are known from both U.S. Pat. No. 3,300,525 and French patent No. 2,031,167 which are obtained from sulfonation and, possibly partial chlorination of unsaturated natural or synthetic fatty acid esters. Sulfur trioxide, mixed with inert gases, if applicable, is used as the sulfonating agent. Due to their content of genuine sulfonates, such sulfonation products are acid-resistant. However, they retain a partially unsaturated character so that a degree of oxidation sensitivity and light sensitivity remains. Also, the sulfonation of unsaturated substances with sulfur trioxide is difficult because of the occurring strong oxidation reaction which makes it hard to prevent dark discolorations and undesired polymerizations. Not even a subsequent treatment of such sulfonates by means of the usual bleaching agents can eliminate the above disadvantages.
U.S. Pat. No. 3,988,247, incorporated herein by reference, discloses fat-liquoring agents for leather or furs based upon sulfonated chlorination products of natural or synthetic higher fatty acids or esters of fatty acids in the form of their alkali metal, ammonium, or amine salts. These agents consist of those sulfonated chlorination products that were obtained by chlorinating higher fatty acids or of esters of higher fatty acids having chain lengths of from 8 to 24 carbon atoms up to a chlorine content of from about 20 to 45 percent by weight, the products of chlorination generally not containing any olefinic double bonds, and subsequently sulfonating said products with SO.sub.3 to attain an SO.sub.3 content of from 40 to 150 mol, based on the products of chlorination.